This invention relates to an attachment device for a metal cutting torch which allows the user to accurately cut circular holes through a metal workpiece.
There have been a number of devices proposed over the years for aiding in cutting circular holes through a metal workpiece. One such device is described in U.S. Pat. No. 4,157,814 issued to Miller. The Miller torch attachment includes an elongated body having a torch tip support member for receiving the torch tip and which can lock the torch tip into place by a thumb screw. The gas lines connected to the other end of the torch merely rest in a U-shaped cradle. A longitudinally adjustable V-shaped scribe member is placed into a hole located at the center of the circle to be cut. In practice the Miller device is not very satisfactory because the gas lines merely rest on the cradle, thereby allowing the torch to twist out of vertical alignment which causes the torch tip to be at an angle to the workpiece resulting in the edges of the hole being cut to not be perpendicular to the planar surfaces of the workpiece.
It is an object of the present invention to provide a circle cutting attachment device for a cutting torch that is locked to the torch in a manner that eliminates any movement of the torch relative to the attachment during use.
The circle cutting torch attachment device includes an elongated rack having a longitudinal axis, a front end, and a rear end. The rack has a lower planar surface with a plurality of gear teeth extending therefrom.
A torch tip sleeve is attached to the front end of the rack. The torch tip sleeve has a body with a cylindrical opening passing therethrough. The cylindrical opening has a longitudinal axis that is at an angle to the vertical.
A cradle arm extends substantially perpendicularly above the rear end of the rack. A U-shaped cradle is attached to the outer end of the cradle arm. The U-shaped cradle is adapted to tightly engage the barrel of a cutting torch.
A centering pin carriage is located on the rack. The rack passes through a channel in the carriage. The carriage has an internally located gear wheel with a plurality of gear teeth positioned and adapted to engage the gear teeth of the rack. The carriage has means for lockingly engaging the rack.
A centering pin extends downwardly from the centering pin carriage, and is adapted to engage and pivot about a guide hole located in the center of a metal workpiece.